User blog comment:Semerone/Den Ei Rai Bu translation blog/@comment-27493717-20170528182646/@comment-27493717-20170602185352

12th Line of Text
The game now shows a flickering, white screen, which shifts to another one, showing an intimidating Mode-7 model of the Diamond Dragon slowly wagging with its tail. Mode-7 is the ancestor of the 3D-engine, giving 2D graphics a more three dimensional look.

とき をこえ, 少たた び まい るベし. 」 (Furigana only) 時 をこえ, 再 び 参 るベし. 」 (Kanji mixed with Furigana)
 * 「こんごうふ を の ぞむとあらば,
 * 「金剛斧 を の ぞむとあらば,
 * (original line)
 * "If you are looking for the Diamond Axe, return to a place beyond time."
 * (translated line)

It's the Diamond Dragon and he gives Chiaki a riddle.

He is obviously referring to time travel. In the anime, Chiaki and the others return to the past, which also happens ingame.